Air conditioning system



March 8, 1938. E. A. BAILEY 2,110,693

AIR CONDITIONING SYSTEM Filed May 26, 1937 nun nun Q Inventor: Edward A B an leg,

b9 $WEJW,

Attorney.

Patented Mar. 8, 1938 PATENT. OFFICE r 2,110,898 AIR oounrnomo srs'rsu Edward A. Bailey, West Caldwell, N. 1., usignor to General Electric Company, a corporation of UNITED STATES New York Application MI! 26, .1987, Serial No. 144,917 Claims. (01. 257-8) therefore necessary to provide some arrangement for removing the frost in order to obtain maximum economy of operation.- Accordingly, it is an object of my invention to provide a system for conditioning the air within an enclosure having a cooling element and an improved arrangement for removing frost collected on the cooling-coil.

Another object of my invention 'is to provide an improved system for heating or cooling the air within an enclosure and an arrangement whereby the heating unit may be utilized to defrost the cooling unit. I

Further objects and advantages of my invention will become apparent as the following description proceeds, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of my invention, reference may be had to the accompanying drawing, the single "figure of which shows diagrammatically an air conditioning system embodying my invention.

Referring now to the drawing, I have shown an air conditioning systemincluding a casing l0 within which isarranged a duct ll provided with an inlet l2 passing through a wall i3 of the enclosure for receiving air from outside the en- 40 closure. A fan i4 driven by a motor i5 is provided for circulating air through the duct ii and into the enclosure through a discharge outlet i6. Within the duct ii are arranged a heating coil or element ll, a cooling coil or element i8 and a hu.

refrigerating machine comprising a compressor 25 driven by a motor 20, a condenser 21 and a liquid receiver 28. Gaseous refrigerant is compressed by the compressor 25 and is discharged into the condenser 21 where it is cooled andliquefied, the liquid refrigerant flowing into and collecting in the receiver 2!. Liquid refrigerant flows from the receiver 28 through a conduit 29 to the cooling coil II. A normally closed solenoid valve 30 is provided in the conduit 28. When the valve 20 is opened, refrigerant flows to the coil l8 and the flow is controlled by a thermostatic expansion valve ii. The valve ii is provided with a bulb 22 filled with a volatile liquid and secured in contact with the outlet conduit of the coil as is well known in the art to control the degree of superheat of the gaseous refrigerant discharged from the coil. The refrigerant vaporized within the coil i8 is returned to the compressor through a suction conduit 23.

The humidifierv l9 comprises a pan 34 below which and within the duct ii is suspended a zigzag wire screen 35. Water is supplied to the pan 24 through a pipe 38, the fiow of water being con trolled by a solenoid valve 31. When water is admitted to the pan 34 it flows from the pan onto the screen 25 through a plurality of orifices in the bottom of the pan. The air flowing through the duct ii passes through the screen 35 and absorbs a portion of the water flowing thereover. The remaining water falls to the bottom of the duct and is drainedtherefrom through a pipe 38.

When there is a demand for heating of the air within the enclosure, heating medium is supplied to the coil II to heat the air passing through the duct ii and into the room. Should there be a demand for increasing the relative humidity of the air. within the room, water will be admitted to the pan 34 of the humidifier. When there is a demand for cooling of the air within the room a solenoid valve 80 and a motor 26 are operated to supply refrigerant to the coil l8 and thereby cool the air passing through the duct and into the room.

In order to initiate the heating and cooling operations of the air conditioning system a thermostat 39 is provided in the enclosure to be conditioned and is arranged to operate heating and cooling relays 40 and 4i respectively dependin on whether there is a demand for heating or for cooling. Power for energizing the motor and control circuits is supplied from lines 42 and 43 metallic member 53 which moves to the left and engages a contact 54 on a demand for heating and moves to the right to engage a contact 55 on a demand for cooling. When the relays 48 and 4| are in the positions shown and the member 53 engages one of the contacts 54 and 55, a circuit is prepared from one side of the secondary 52' through a connection 56 and one of the coils 51 and 58 of the relays 48 and 4| respectively through the member 53, a bridging member 59 of a relay 68 and a line 6| to a contact 62. A time controlled mechanism 63 is provided to test the thermostat circuit periodically and if there is a demand for heating or cooling to energize the circuit and operate one of the relays 48 and 4| as selected by the thermostat 39. The time controlled device 63 comprises two cams 64 and 65 mounted upon a shaft driven by a synchronous motor 66 connected across the lines 42 and 43 by lines 61 and 68 respectively. The motor 66 may be selected, for example, to rotate the cams 64 and 65 at a speed of one revolution per minute so that the thermostat circuit is tested once in every minute to determine whether one of the relays 48 and 4| should be operated or released. The cam 65 is provided with a raised portion 69 and the cam 64 is provided with a recessed portion 18 corresponding in position to the raised portion 69. Cam 64 operates a movable contact member 1| and the cam 65 operates a movable contact member 12. The raised portion 69 lifts the contact member 12 to engage the contact 62 and connect the line 6| through a connection 13 to the secondary 52 of a transformer. If the thermostat-member 53 is in engagement with eitherof the contacts 54 and 55 at this time a circuit will be completed through one of the coils 51 and 58 and one of the relays 48 and 4| will be operated. The recessed portion 18 is somewhat shorter than the raised portion 69. For example, the raised portion 69 may correspond to a time of five seconds and the recessed portion 18 to a time of two seconds. .The purpose of the cam 64 and the contact member 1| is to provide a holding circuit for the relay coils 51 and 58. This holding circuit is broken while the recessed portion 18 is engaging the movable member 1|. It will be seen that the members 1| and 12 will both be in engagement with their contacts Ho and 62 respectively for a period of one and one-half seconds at either end of the time during which the cam surface 69 engages the member 12. If the relay coils are energized during this time they will be maintained energized throughout the remainder of the period of rotation of the cams since the holding circuit will be maintained closed from connection 13 through member 1| and a line 14.

During the operation of the air conditioning system, should the member 53 of thermostat 39 be in engagement with the contact 54 when the cam 65 moves the member 12 against the contact 62 the coil 51 of relay 48 will be energized to raise an armature 15 and relay arms 16 and 11. Arm 16 engages a contact 18 and closes theholding circuit for coil 51 from line 14 through an arm 19 and a contact 88 of relay 4| and a connection 8| to the coil 51 through a line 82 which connects coil 51 and contact 54. A lower arm 11 of the relay closes a circuit from line 42 through a connection 83, a contact 84 and a line 85 and a contact 86 through a cam operated switch member 81 to the motor 24, the motor being connected to the line 43 through line 48. Motor 24 is thereby energized and operates to open valve 23.for supplying heating medium to the coil I1. A cam 88 driven by the motor rotates and moves the member 81 away from the contact 86 to open the motor circuit when the valve 23 has been opened, and allows a movable switch member 88 to engage a contact 89a and prepare a motor circuit through the movablemember 89 and a line 98 to a contact 9| of the relay 48. At a subsequent rotation of the cams 64 and 65 into position to move the arms 1| and 12 should member 53 not be in engagement with contact 54 the relay circuit will .be broken and the relay coil 51 deenergized allowing the armature 15 to drop out. In the drop-out position the arm 16 opens the holding circuit of the coil 51 and the arm 11 closes a circuit to the motor 24 upon engagement with the contact 9|. The motor 24 thereupon rotates to close the valve 23 and the cam 88 restores the movable members 81 and 89 --to the positions shown in the drawing.

Upon a demand for cooling of the air within the room to be conditioned the movable member 53 of thermostat 39 engages contact 55 and the cams 64 and 65 close the operating and holding I 19 in its raised position engages a contact 94 to I close the holding circuit from the line 14 through the arm and a connection 95 to the coil 58. The lower arm 93 engages a contact 96 to complete a circuit from the line 43 through a line 91, arm 93, contact 96 and a line 98 to energize a coil 99 of solenoid valve 38, the circuit being completed from coil 99 through a line I88 and line 41. Connected in parallel with the coil 99 across the lines 98 and I88 is a coil I8| of a switch I82 controlling the motor 26. Energization of the coil 99 raises an armature I83 and opens the valve 38. Energization of coil I8I closes the switch I82 to connect motor 26 to lines 42 and 48 through connections I84 and I85 respectively. The refrigerating machine is thereby set in operation to supply liquid refrigerant to the cooling coil I8 through the thermostatic expansion valve 3|, and the air passing through the duct II is thereby cooled. On a subsequent rotation of the earns 64 and 65 should the thermostat member 53 be out of engagement with the contact 55 the coil 58 will be deenergized thereby deenergizing the coils 99 and |8I and stopping the operation of the refrigerating machine.

When it is desired to increase the relative humidity of the air within the room to be conditioned the humidistat I86 is operated to open the valve 31 and admit water to the pan 34. The humidistat I86 comprises a movable member 81 which engages a contact I88 upon a demand for humidity increase and the contact I89 when the humidity has increased to the desired value. When the member I81 engages the contact I88 a circuit is completed from the secondary 52 of the transformer 58 through the contact I88 and member I81 to a coil 8 of a switch I. Energization of the coil 8 raises an armature H2 and switch arms 3 and 4 are raised to engage their contacts. The arm I I3 closes a holding cir cuit for the coil 8 through a connection 5.

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member I01 engages the contact I09 and shortsout the coil IIO through a connection III. Ar-

mature II2 then drops out and opens the circuit to coil II! to stop the flow of water to the pan 3!.

During the operation of the cooling coil I8, moisture is condensed from the air circulating through the duct II and when the cooling coil is operated at temperatures below freezing the moisture forms a coating of frost on the coil. In order periodically to remove the accumulation of frost, I provide an arrangement whereby the supply of cooling medium to the coil I8 is interrupted for a predetermined length of time while heating medium is supplied to the coil II. The air passing through the duct II is then heated by the coil I1 and in passing over the coil I8 melts the accumulation of frost which flows to the bottom of the duct and is drained out through a pipe IIQ.

In order to effect this periodic defrosting of the coil I8, I provide a time controlled mechanism I comprising a synchronous motor I2I arranged to drive a cam I22 which periodically moves a contact member I23 into engagement with a stationary contact I24, the cam I22 being provided with a raised portion I28 which moves the. member I23 against the contact I24. The cam I22 may, for example, be designed to operate the movable switch member I23 so that it holds the switch member in engagement with the contact I24 for a period of about two minutes every four hours to defrost the coil I8 and maintain a minimum accumulation of .frost. When the member I23 engages the contact I24 a circuit is closed from a line I28 through the member I23 and the contact I24 to a coil I 21 of the relay ill and back to the supply line through a line I28. Energization of the coil I21 raises an armature I29 and lifts switch member 58 to engage a stationary contact I30. Raising of the switch member 59 breaks the connection between the line BI and the thermostatic member 53, and establishes a connection between the line 6i and the line 82, so that the coil 51 of the heating relay 40 is placed in the relay operating circuit and is actuated upon rotation of the cams 64 and 65, in the same manner as previously disclosed, with reference to the moving of the thermostatic member 53 into engagement with the contact 54in response to a demand for heating of the air within the enclosure. Since the connection to the thermostatic member 53 has been broken, the cooling relay 4I cannot be energized and the refrigerating machine is stopped so that no refrigerant is supplied to the coil l8. Since the fan I4 operates continuously air is circulated through the duct I I over the coil I1 and is thereby heated before flowing over the coil I8. The heated air melts any accumulation of frost on the coil I3 and is cooled thereby before being discharged into the room. There is, therefore, no appreciable heating of the air in the room during the short period required for defrosting. As soon as the cam I22 rotates to move the raised portion I23 away from the member I23, the circuit of the coil I21 is broken and the armature I29 drops out to restore normal operation of the system under the control of the thermostat 33. The defrosting operation is thus effected with a-minimum of additional control apparatus and no additional heating units are required in the air conditioning system.

From the foregoing, it is apparent that I have provided an improved air conditioning system for heating and cooling the air within an enclosure, which includes a simple and effective arrangement for periodically defrosting the cooling coil.

Although I have described my invention in connection with a particular air conditioning system, other arrangements will readily be apparent to those skilled in the art. I do not, therefore, desire my invention to be limited to the construction shown and described and I intend in the appended claims to cover all modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:-

1. A system for conditioning the air within an enclosure including a duct, a heating element associated with said duct, a cooling element associated with said duct, means for circulating air continuously through said duct and for discharging a portion of said air into said enclosure to cool the air within said enclosure, means for supplying heating medium to said heating element, means for supplying cooling medium to said cooling element whereby moisture may be condensed from said circulating air and frost may be formed on said cooling element, means responsive to the temperature of the air within said enclosure for controlling said cooling medium supplying means. and means for periodically stopping automatically the supply of cooling medium to said coolin element and for starting the supply of heating medium to said heating element to melt the frost on said cooling element.

2. A system for conditioning the air within an enclosure including a duct, a heating element in said duct, a cooling element in said duct, means for circulating air continuously through said duct first over said heating element and then over said cooling element and for discharging a portion of said air into said enclosure to cool the air within said enclosure, means for supplying heating medium to said heating element, means for supplying cooling medium to said cooling element whereby moisture may be condensed from said circulating air and frost may be formed on said cooling element, means responsive to the temperature of the air within said enclosure for controlling said cooling medium supplying means, and means for periodically stopping automatically the supply of cooling medium to said cooling element and for starting the supply of heating medium to said heating element to heat the air passing through said duct and to melt the frost on said cooling element.

3. A system for conditioning the air within an enclosure including a duct, a heating element in said duct, a cooling element in said duct,

means for circulating air continuously through said duct first over said heating element and then over said cooling element and for discharging a may be formed on said cooling element, means dependent upon a demand for heating of the air within said enclosure for controlling said heating medium supplying means, means dependent upon a demand for cooling of the air within said enclosure for controlling said cooling medium supplying means, and means operable automatically for periodically preventing the supplying of cooling medium to said cooling element and for actuating said heating medium supply means to heat the air passing through said duct and to melt the frost on said cooling element.

4. A system for conditioning the air within an enclosure including a duct, a heating element in said duct, a cooling element in said duct, means for circulating air continuously through said duct first over said heating element and then over said cooling element and for discharging a portion of said air into said enclosure, means for supplying heating medium to said heating element, means for supplying cooling medium to said cooling element whereby moisture may be condensed from said circulating air and frost may be formed on said cooling element. means responsive to the temperature of the air within said enclosure for selectively actuating said cooling medium supplying means and said heating medium supplying means to heat and to cool the air circulating through said duct, and means cooperating with said temperature responsive means for periodically stopping automatically the supply of cooling medium to said cooling element and for starting the supply of heating medium to said heating element to heat the air passing through said duct and to melt the frost on said cooling element.

5. A system for conditioning the air within an enclosure including a duct, a heating coil in said duct, a cooling coil in said duct, means including a fan for circulating air continuously through saidduct first over said heating coil and then over said cooling coil and for discharging a portion of said air into said enclosure, means for supplylng heating medium to said heating coil, means for supplying cooling medium to said cooling coil, means for maintaining said cooling coil at temperatures below freezing whereby frost may be formed on said cooling coil, means including a thermostat responsive to the temperature of the air within said enclosure for selectively actuating said cooling medium supplying means and said heating medium supplying means dependent upon demands for heating and for cooling of the air within said enclosure, and time controlled means cooperating with said temperature responsive means for periodically preventing the supplying of cooling medium to said cooling coil and for actuating said heating medium supplying means to heat the air passing through said duct and to melt the frost on said cooling element.

EDWARD A. BAILEY. 

